The present invention relates to an apparatus and method of forming a liquid film of a development solution for processing a thin film coated on a substrate.
In a photolithographic process for manufacturing a semiconductor device, a photoresist is coated on a wafer surface, and the resultant photoresist coating film is pattern-exposed and then developed by being exposed to a developing solution. In a conventionally-employed developing method (shown in FIGS. 1 and 2), a wafer W is vacuum-adsorbed by a spin chuck 111 and a supply nozzle 113 is positioned in such a way that spray holes 112 are placed in the proximity of an upper central portion of the wafer W. The supply nozzle 113, which has a length substantially equal to a diameter of wafer W, has numerous spray holes 112 arranged linearly along the longitudinal direction of the supply nozzle 113. A developing solution 10 is simultaneously sprayed from the numerous spray holes 112 to the wafer W, thereby mounting the developing solution 10 on the wafer W, as shown in FIG. 1. Thereafter, the wafer W is rotated by an angle of 180.degree. while continuously supplying the developing solution 10 from the supply holes 112. In this way, a film of the developing solution 10 is formed over an entire surface of the wafer W. Note that the wafer must not be rotated in excess of 180.degree. in order to prevent an initially supplied developing solution (proceeding developing solution) from being contaminated with a newly supplied developing solution (following developing solution). If the proceeding developing solution is contaminated with the following developing solution, a contaminated portion differs in resolution from a non-contaminated portion. As a result, the film is not developed uniformly.
However, the conventionally-employed method has the following problems. Before the developing solution is sprayed from the supply nozzle 113 to the wafer W, a predetermined amount of the developing solution is sprayed and discarded into the drain cup. This is called "dummy dispense". However, when the "dummy dispense" is carried out, liquid drops are attached to a tip portion of the supply nozzle 113 (i.e., around the spray holes 112), and the particles floating in the air are sometimes attached to the liquid drops. When the liquid drops are dried, the particles may drop on the wafer W, contaminating the wafer W.
The developing solution 10 is supplied by blowing a pressurized gas into a developing solution tank. The pressurized gas pushes out the developing solution 10 from the developing solution tank toward the supply nozzle 113. Therefore, gaseous ingredients of the pressurized gas are dissolved in the developing solution 10. The dissolved gaseous ingredients appear as micro bubbles on the wafer surface after the developing solution is sprayed. Due to the presence of micro bubbles, some regions of the film are not developed well (due to resolution impossible) or developed insufficiently (due to insufficient resolution), leading to developing defects. Since the wiring width of the circuit pattern has been reduced more and more in the recent days, the developing defect, even it is small, results in a fetal damage.
Another method is proposed as shown in FIG. 3. In the method, the supply nozzle 113 is placed along an orientation flat (O. F.) of the wafer W. The developing solution 10 is allowed to spray toward a non-pattern formation region outside the pattern formation region. Subsequently, the supply nozzle 113 is scan-moved along the surface of the wafer W in a Y-axis direction while spraying the developing solution. However, the length of the orientation flat (O. F.) is shorter than the diameter of the wafer W, the initially mounted developing solution 10 is spread sideward. Consequently, no developing solution 10 is applied in some regions and the developing solution 10 is applied but insufficient in other regions. In this case, even if the developing solution 10 is supplied from the nozzle 113 in a larger amount, the same phenomena are resulted. As a result, the film is not developed uniformly. Furthermore, in the case where a large-size (e.g., 12 inches) wafer W is used, a V notch 88 (shown in FIG. 16) is employed as crystal-orientation identification means in place of the orientation flat (O. F.). Therefore, the developing solution is initially mounted on an inevitably narrower space, resulting in non-uniform development.